Japan Tobacco is suing the Thai government over plans to introduce bigger and more prominent anti-smoking warnings on cigarette packets, the company says, as rival Philip Morris vows similar action.

The Tokyo-based firm, one of the world's biggest cigarette companies, with brands including Winston and Benson & Hedges, said the planned changes from Thailand's public health ministry would interfere with its operations in the kingdom.

Thailand has decided to extend health warnings from 50 to 85 per cent on both sides of every cigarette packet sold in the country. The new rule is to come into effect in October, but Japan Tobacco said the change would have a "disproportionate impact on legitimate competition, intellectual property rights and freedom of expression".

"In order to protect its ability to continue to use its brands and key trademarks in Thailand, JTI (Japan Tobacco International) has initiated a legal challenge against this notification," the company said in a statement on Wednesday, referring to a lawsuit filed in Thailand on June 19.

The company added that adult smokers should be "appropriately informed" before deciding to smoke and smokers "should continue to be reminded" about the health risks.

"JTI however does not believe that increasing the size of graphic health warnings to cover 85 per cent of cigarette packaging is effective or proportionate," it added.

Philip Morris, which makes the Marlboro brand, and hundreds of Thai retailers on Tuesday warned they would sue Thai health authorities and claimed the industry was not consulted on the changes from Thailand's health ministry.

Philip Morris has fought bitter legal battles with governments before, most famously losing an action against the Australian government to introduce entirely plain cigarette packaging with the same typeface and graphic images of diseased smokers.